Indicator components for microfluidic systems

ABSTRACT

Microfluidic devices and systems that include keying, registration or indication elements that communicate a functionality of the microfluidic device to the instrumentation which is used in conjunction with these devices. Indicator elements include structural indicators, electrical indicators, optical indicators and chemical indicators. Different indicator elements are indicative of different functionalities, e.g., applications, new vs. used, and the like.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/377,681 filed Aug. 19, 1999, the disclosure of which isincorporated herein in its entirety.

BACKGROUND OF THE INVENTION

[0002] Microfluidic devices and systems have advanced rapidly fromacademic postulations to functioning commercial research products thatare actively contributing to the research and development ofpharmaceutical and other biotechnological and chemical products.

[0003] Examples of microfluidic devices and systems for performing avariety of different operations are described in, e.g., WO 98/00231, WO98/05424, WO 98/22811, WO 98/46438 and WO 98/49548, all of which areincorporated herein by reference in their entirety for all purposes.Such microfluidic systems are generally configurable to performvirtually any operation, assay or experiment previously performed at thelaboratory bench, but with a greater degree of accuracy, speed andautomatability. Specifically, because microfluidic systems are performedin such small spaces, reagent quantities, an mixing times aresubstantially reduced. Further, because of the integrated nature ofmicrofluidic systems, e.g., channel networks fabricated in a singlechip, multiple different operations can be incorporated into a singledevice and controlled by an automated control and detection system. Theavailability of automated instrumentation, in turn, provides forunparalleled reproducibility as compared to bench scale operations,which rely upon measurements and judgements of human operators.

[0004] It is generally desirable to be able to automate more and moreoperations that are to be performed within a laboratory. Whilemicrofluidic systems, in general, contribute substantially to thisautomation desire, there exits a number of other operations that can beautomated in conjunction with the use of these devices. The presentinvention provides apparatuses systems and methods that furthercontribute to this automation trend.

SUMMARY OF THE INVENTION

[0005] In a first aspect, the present invention provides a microfluidicdevice comprising a body structure configured to interface with a baseinstrument. The body structure includes microfluidic elements and anindicator element fabricated into the body structure. The indicatorelement provides an indication to an instrument of a functionality ofthe microfluidic device.

[0006] Another aspect of the present invention is a microfluidic systemcomprising a controller instrument. The controller instrument iscomprised of a microfluidic device nesting region having an interfacearray for operably coupling one or more of a material transport systemand a detector disposed within the controller instrument with amicrofluidic device placed in the nesting region. The system alsoincludes a microfluidic device having a body structure. The bodystructure includes an indicator element. The indicator element providesan indication to the instrument of a functionality of the microfluidicdevice.

BRIEF DESCRIPTION OF THE FIGURES

[0007]FIG. 1 schematically illustrates an overall microfluidic analysissystem.

[0008]FIG. 2 schematically illustrates a microfluidic device.

[0009]FIG. 3 schematically illustrates the device registration elementsof the present invention. FIG. 3A shows a microfluidic device thatincludes a number of different registration elements as describedherein. FIG. 3B shows a view of a portion of the overall instrumentincluding the interface portion that includes the device corral with oneexample of registration elements. FIG. 3C is an exploded view of thenesting region of an instrument similar to that shown in FIG. 3B,showing the registration elements.

[0010]FIG. 4 is an alternate schematic illustration of a microfluidicdevice and accompanying instrument that comprise mechanical indicatorelements/registration structures.

[0011]FIG. 5 schematically illustrates one example of a microfluidicdevice incorporating an electrical indicator element according to thepresent invention.

[0012]FIG. 6 schematically illustrates a microfluidic device includingan optical indicator element and accompanying instrument.

DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention permits greater automatability byconfiguring the device to communicate one or more functionalities of themicrofluidic device to instrumentation, and particularly controllingand/or detection instrumentation, to facilitate the operation of thecombination of the device and instrumentation.

[0014] As used herein, a “functionality” of a microfluidic device refersto the use to which the device will be or has been put. The indicatedfunctionality of a device may range from the relatively general, e.g.,for performing multi-sample separations, to more specific, e.g.,performing kinetic assay on a protein kinase sample. Thus, as typicallyused, the functionality refers to the application for the device.However, the term “functionality” as used herein, also includes whethera device is functional for any application in the first instance, e.g.,whether the device is nonfunctional as a previously used device.

[0015] Typically, from application to application, microfluidic devicesand systems rely upon many of the same means to carry out the desiredoperation, e.g., in fluid or material movement, mixing etc., as well asdetection of operation results. As such, instrumentation for operatingthese systems is generally standardizable, with the devices themselves,the chemistries placed in those devices, and the timing of reagentmixtures yielding distinctions between different operations.

[0016] For these standard instruments, different operating parameters,e.g., for performing different operations must generally bepreprogrammed into the instrument or computers that control operation ofthe instruments. Of course it is still incumbent upon the user toidentify for the instrument when a different application is to beperformed. In accordance with the present invention, however, amicrofluidic device is configured with an indicator element whichindicates to the instrument the functionality of the device that isinterfaced with the instrument, e.g., the specific type of assay orother application that is to be performed, or whether the device hasbeen previously used. The instrument then typically adjusts for carryingout the operation of the device interfaced with it. For example, theinstrument may select from different available detection modes, e.g.,fluorescence wavelengths, UV transmittance, etc., as well as differentavailable material transport means, e.g., pressure based fluidtransport, electrokinetic transport or hybrid pressure/electrokineticsystems. For specifically identified functionalities, e.g., specificseparations, enzyme assay or the like, the instrument also optionallyimplements control profiles, e.g., a script for directing fluids orother materials through specific channels at specific times and/or inspecific ratios, volumes and/or flow rates.

[0017] An overall system including a microfluidic device and itsassociated instrumentation is illustrated in FIG. 1. As shown, thesystem includes a microfluidic device 100, which is selected from a menuof devices having different functionalities, e.g., devices 100-106. Asdescribed in greater detail below, the microfluidic device typicallyincludes an indicator element to communicate to the instrumentation ofthe system the functionality of that device. The system also typicallyincludes a controller detector instrument 108, upon or into which thedevice is placed for operating the device. Once mounted on theinstrument, detector 110 is disposed adjacent to the device 100 andwithin sensory communication of the channels disposed in the device, inorder to detect results of reactions within those channels. As usedherein “within sensory communication” refers to a detector that ispositioned to receive a signal from a channel of the microfluidicdevice, typically at a detection window. Such signals include opticalsignals, thermal signals, electrical signals, and the like. In eachcase, the detector is placed such that the detection aspect of thedetector, e.g., a sensor, is placed so as to receive the appropriatetype of signal from the channel. In the case of optical signals, thedetector is typically placed adjacent to a transparent region of thechannel with the optical elements positioned to receive an opticalsignal and detect that signal. In the case of electrical detectors, asensor is typically disposed within the channel in order to be withinsensory communication.

[0018] Controller 120, also disposed in the instrument 108, controls themovement of materials through the channels and/or chambers of themicrofluidic device in order to carry out the device's prescribedfunctionality. A computer or processor 130 is also typically provided toinstruct the operation of the controller 120 in response to user inputor programmed commands. The computer 130 also typically receives datafrom the detector 110, stores and/or analyzes the data to provideinformation to the user in a readily understandable format. Althoughillustrated as a separate element, it will be appreciated that thecomputer or processor 130 may be integrated into the instrument 108 aswell.

[0019] As used herein, a “microfluidic device” refers to a device thatincludes at least one fluidic element, e.g., channel, chamber, reservoiror the like, that has at least one cross sectional dimension in themicroscale range, e.g., between about 0.1 and about 1000 μm. Typically,such devices include networks of channels and/or chambers that areinterconnected, and through which a variety of different fluids or othermaterials are transported. These devices are used to mix, separate,react and otherwise manipulate sample reagents and other materials inperforming a variety of chemical, biochemical and biological analyses.Microfluidic devices may be fabricated in a variety of different ways.For example, a device may be fabricated as an aggregation of differentparts, e.g., capillaries, reaction chambers, etc., that are piecedtogether to form a desired network of channels and/or chambers. Inpreferred aspects however, microfluidic devices are assembled from anaggregation of planar layers to form a single integrated microfluidicdevice that includes the channels and chambers within its interiorportion.

[0020] One example of a microfluidic device is illustrated in FIG. 2.Specifically, FIG. 2 illustrates the layered construction of preferredmicrofluidic devices. As shown, the device body structure 200 isfabricated from two or more layers 202 and 208. In particular, thebottom portion of the device 202 comprises a solid substrate that issubstantially planar in structure, and which has at least onesubstantially flat upper surface 204. The channels and/or chambers ofthe microfluidic devices are typically fabricated into the upper surfaceof the bottom substrate or portion 202, as microscale grooves orindentations 206, using the above described microfabrication techniques.The top portion or substrate 208 also comprises a first planar surface210, and a second surface 212 opposite the first planar surface 210. Inthe microfluidic devices prepared in accordance with the methodsdescribed herein, the top portion also includes a plurality ofapertures, holes or ports 214 disposed therethrough, e.g., from thefirst planar surface 210 to the second surface 212 opposite the firstplanar surface.

[0021] The first planar surface 210 of the top substrate 208 is thenmated, e.g., placed into contact with, and bonded to the planar surface204 of the bottom substrate 202, covering and sealing the grooves and/orindentations 206 in the surface of the bottom substrate, to form thechannels and/or chambers (i.e., the interior portion) of the device atthe interface of these two components. The holes 204 in the top portionof the device are oriented such that they are in communication with atleast one of the channels and/or chambers formed in the interior portionof the device from the grooves or indentations in the bottom substrate.In the completed device, these holes function as reservoirs forfacilitating fluid or material introduction into the channels orchambers of the interior portion of the device, as well as providingports at which electrodes may be placed into contact with fluids withinthe device, allowing application of electric fields along the channelsof the device to control and direct fluid transport within the device.

[0022] These devices may be used in a variety of applications,including, e.g., the performance of high throughput screening assays indrug discovery, immunoassays, diagnostics, genetic analysis, and thelike, e.g., as described in Published International Patent ApplicationNo. 98/00231 and U.S. Pat. No. 5,779,868 each of which is herebyincorporated by reference in its entirety for all purposes.

[0023] Indicator elements fabricated or otherwise disposed within amicrofluidic device may take on a variety of forms, including mechanicalindicator elements, electrical indicator elements, optical indicatorelements and chemical indicator elements. The specific type of indicatorelement used in a particular device is mirrored by a complementarydetection element upon the instrument which is interfaced with thedevice.

[0024] Mechanical indicator elements typically comprise a registrationstructure or collection of registration structures or structuralelements fabricated onto, into or attached to the body of themicrofluidic device. The registration structures on the device mate withor otherwise engage elements upon the nesting region of an instrument.The elements upon the instrument may include complementary registrationstructures which are configured only to receive the registrationstructures of a particular device, e.g., having a specific application.In such cases, only one type of device will be permitted to interfacewith the nesting region or adapter element of the instrument, as otherdevices will not possess the same complementary registration elements orstructures. In order to interface a different device with theinstrument, one is required to swap out the adapter element/nestingregion for an adapter having the appropriate registration structures.The use of interchangeable adapter elements for interfacing differentmicrofluidic devices to a common instrument platform has been previouslydescribed in, e.g., published International Patent Application No. WO98/05424, which is incorporated herein by reference in its entirety forall purposes.

[0025] A variety of registration or indicator structures are optionallyemployed in this aspect of the present invention. For example, a seriesof pins, posts, blocks, tabs, etc. may be disposed upon the surface ofthe nesting region of the instrument. A corresponding and complementaryseries of holes, depressions, notches, cavities are then disposed on thedevice to receive the structures on the instrument when the microfluidicdevice is appropriately oriented on the nesting region. Althoughdescribed as positive structures, e.g., protrusions, being disposed onthe instrument and negative structures, e.g., depressions, beingdisposed on the microfluidic device, it will be appreciated that thecomplementary structures may be disposed upon either the device or theinstrument.

[0026] Alternatively or additionally, the microfluidic device mayincorporate at least one shaped edge, e.g., having a unique contour,that is complementary to an edge of the nesting region, such that absentthe appropriately shaped edge, the microfluidic device will not beinsertable into the nesting region of the instrument.

[0027]FIG. 3 schematically illustrates an example of aregistration/indicator structure on a microfluidic device and itscontroller/detector instrument. FIG. 3A illustrates the microfluidicdevice 300 that includes a number of exemplary registration structures,from a number of views (top, side, end and perspective). As shown, thedevice 300 includes a body structure 302 which includes a microfluidicsubstrate attached or integral thereto (not shown). The body structureincludes ports or reservoirs 304 disposed thereon which are in fluidcommunication with the channel elements of the microfluidic device. Thebody structure of the device also includes a number of registrationstructures, e.g., notch 306 and truncated corner 308, which provide anindication of the functionality of the microfluidic device, e.g., theparticular application for which the device is used, i.e., nucleic acidseparations, protein separations, enzyme assays, cellular functionassays and the like. Specifically, the position, number and or size ofthe registration structures is typically varied from a device of onefunctionality to a device of another functionality. For example,although illustrated with a single notch 306 along one edge of the bodystructure 302, multiple notches, or different size notches areoptionally used along the same edge or different edges of the bodystructure to identify the functionality of the overall device.

[0028] A complementary structure or set of structures on the instrumentis used to ensure that the instrument is appropriately configured tointerface, control and monitor the functionality, e.g., the application,of the microfluidic device inserted therein. FIG. 3B illustrates aportion of an example of a controller detector instrument 320 thatincludes a nesting region 322 onto which the device 300 is mounted.

[0029] A lid 324 is rotatably attached to the instrument 320. Theunderside of the lid 326 typically includes a number of interfaceelements for controlling the functioning of the device. For example, asshown, a plurality of electrodes 328 are provided attached to theunderside 326 of the lid 324. These electrodes 328 rotate intocommunication with fluids in the reservoirs 304 in the body structure ofdevice 300. These electrodes 328 that are operably coupled to powersources (not shown) within the instrument 320, provide actuation ofmaterial movement within the channels of the device 300 viaelectrokinetic forces. Although shown as electrodes 328, otherinterfaces are optionally or additionally provided in the lid. Forexample, in certain preferred aspects, one or more vacuum or pressureports are provided in the lid with appropriate connectors forinterfacing with one or more reservoirs 304 of the device 300, in orderto provide material movement by pressure induced flow. These vacuum orpressure ports are operably coupled to vacuum or pressure pumps disposedwithin the instrument 320. As shown, at least a portion of the lid 324is removable and replaceable, in order to reconfigure the instrument tointerface with a wide range of different devices. In particular,interface cassette 324 a, which includes the array of electrodes 328, isremovable from lid 324, and a different cassette may be inserted in itsplace. This three-tier instrument architecture (e.g., device, instrumentand removable interface adapter) is described in detail in PublishedInternational Patent Application No. WO 98/05424, which is incorporatedherein by reference.

[0030]FIG. 3C shows an exploded view of a nesting region shown in FIG.3B, absent a microfluidic device. As shown, the nesting region 322includes a microfluidic device “corral” 330 which functions to bothorient the device 300 upon the nesting region, and ensure that theinstrument 320 is appropriately configured for the functionality of thedevice 300. Orientation of the device is provided, inter alia, by anumber of structures on the nesting region, including barrier 332,alignment pins 334, and barrier 336. The presence of these orientationstructures ensures that a device 300 placed into the nesting region 322is appropriately positioned such that the collection lens 338 of adetector disposed in the instrument (not shown) is placed adjacent toand in sensory communication with a relevant channel of the microfluidicdevice 300. Proper orientation is also desirable to provide for properinterfacing of other elements of the instrument with the microfluidicdevice, e.g., heating element or heat sink 340, and flow actuationelements in the lid 324, e.g., electrodes 328.

[0031] As shown, barrier 336 includes additional structural elementsthat are used to both align the device 300 in the nesting region 322, aswell as provide an indication of the functionality of the device 300 tobe used, e.g., which the instrument is configured to run at a particulargiven time. In particular, the interior edge 338 of barrier 336 definesone boundary of corral 330 against which a microfluidic device ispositioned. As shown, a first tab 348 is provided extending into thecorral 330. The tab 348 is positioned and sized to fit within the notch306 that is disposed along the edge of the microfluidic device 300. Theinterior edge 338 of barrier 336 also defines a truncated corner 342that corresponds and is complementary to the truncated corner 308 ofdevice 300. As shown, barrier 336 also includes structural registrationelements that communicate the functionality of the device to theinstrument. In particular, posts 344 and 346 are disposed on barrier336. These posts are positioned and sized (e.g., diameter, height etc.)to indicate the particular functionality of the microfluidic device towhich they are applied. As shown, post 344 is thinner and taller thanpost 346. With reference to FIG. 3B, these posts 344 and 346 arepositioned to mate with corresponding apertures or cavities 344 a and346 a, respectively, in interface cassette 324 a or optionally lid 324.The complementary nature of posts 344, 346 and cavities 344 a and 346 a,ensures that the interface cassette 324 a inserted into lid 324 isappropriate for the particular device 300, as indicated by theregistration structures on barrier 336, e.g., notch 306, and posts 344and 346. In preferred aspects, a portion or all of barrier 336 isremovable (e.g., barrier portion 336 a), allowing for substitution witha barrier that includes different registration elements, e.g., numbersand sizes of notches, posts and the like. In operation, microfluidicdevices having different functionalities include different registrationstructures on their body structure, which registration structures areindicative of the functionality of the device. When a device having adifferent functionality is to be run on an instrument, one replaces thebarrier 336 with a new barrier having registration structurescomplementary to the functionally desired device, and also substitutesthe interface cassette with an appropriate interface for the new device,e.g., electrode configuration, vacuum or pressure ports, etc. Certain ofthe registration structures on the cassette 324 a and barrier 336cooperate to ensure that both the cassette and the barrier areappropriate for the device to be run. Improper cooperation of theseelements can lead to damaging of elements of the device and/or theinterface cassette, e.g., bending electrodes, damaging optics, etc.Proper alignment of the microfluidic device in the nesting region isshown in FIG. 3D.

[0032] Thus, in accordance with the above-described aspect of thepresent invention, “indication of a device's functionality to theinstrument” is provided by an ability to close lid 324 over the device300, e.g., improper interfacing of a device and an instrument isprevented by structural interference of one or more of the registrationelements, e.g., as between device 300 and barrier 336 and/or betweenbarrier 336 and interface cassette 324 a. Thus, this “indication”encompasses both more active communication between the device and theinstrument, as described in greater detail herein, as well as passivecommunication, e.g., as described with reference to FIG. 3.

[0033]FIG. 4 schematically illustrates alternate examples of amicrofluidic device having mechanical indicator or registrationelements, as described herein. As shown, a microfluidic device bodystructure 400 (shown from a side view), is provided having a series ofnotches 404-412 disposed in its lower surface 402. The arrangement, sizeand shape of these notches 404-412 is selected depending upon theparticular application or functionality of the microfluidic device. Forexample, as shown, the body structure includes narrow notches 404, 406and 410 and wider notches 408 and 412. The notches 404-412 on the bodystructure 400 correspond and are generally complementary to registrationstructures disposed upon the nesting region 452 of a controller/detectorinstrument (not shown). As shown, these registration structures include,e.g., posts 454-462, which are provided in a position and of a size suchthat when the body structure is placed upon the nesting region, thenotches 404-412 engage or receive the posts in a fitted fashion,securing the body structure in position, e.g., as shown in Panel A.Further, interaction among these two elements is only generally possiblewhere these structures are complementary. As a result, the functionalityof the microfluidic device, e.g., as indicated by the indicatorstructures, is communicated to the instrument through the inclusion of aproper nesting region 452, e.g., in an appropriate adapter element.

[0034] Optionally, the elements on the instrument that are engaged bythe registration elements comprise displaceable elements that aredisplaced by the registration structures on the device (or are notdisplaced where the registration structure comprises a notch, slot,groove or cavity). Specifically, such elements typically comprise pins,tabs or other structures within the nesting region of the device, thatare spring mounted such that they are normally extended into the nestingregion of the device, but whereby presence of the device in the nestingregion displaces some or all of these elements. Typically, thesedisplaceable elements are also operably coupled to the control orprocessor elements of the instrument, whereby displacement of an elementis detected by the instrument, e.g., through the completion or breakingof an electrical circuit within the instrument. The identity and numberof the plurality of these displaceable elements that is displaced by theregistration structures of a particular device serves as anidentification code for that device. In this manner, the registrationstructures on the device function as a key which, based upon theidentity and number of elements displaced, indicates to the instrument,the functionality of the microfluidic device.

[0035] This alternative aspect is shown in Panel B of FIG. 4.Specifically, the registration structures on the nesting region 452comprise an array of movable or displaceable elements, e.g., posts464-498, which are deflectable upon interaction with the indicatorstructures on the body structure 400. For example, as shown, the nestingregion 450 includes an array of deflectable posts 464-498 extending intothe nesting region. When a device's body structure 400 is placed ontothe nesting region, the indicator structures on the body 400, e.g.,notches 404-412 deflect the posts in a pattern reflective of thoseindicator structures, e.g., only posts 66, 72-76, 82-86 and 90-92 aredeflected. The deflection or lack of deflection of each post is detectedby the instrument. As a result, the functionality of the device, asindicated by the arrangement, size and position of notches (or otherindicator structures), is communicated to the instrument by virtue ofthe number and identity of the posts that are deflected by the body ofthe device. In this latter aspect, the “indication” of a device'sfunctionality is more of an active communication between the device andthe instrument, e.g., by virtue of the device's active deflection ofcertain structures (“switches”) on the instrument. The instrument thenconfigures itself, e.g., via software or firmware programming, to runthe device mounted thereon.

[0036] In alternate aspects, the indicator elements fabricated into orotherwise disposed on or within the microfluidic devices, compriseelectrical indicator elements. The electrical indicator elementsdescribed herein may be passive or active electrical elements. Inpreferred aspects, the electrical indicators are passive, e.g., havingno internal power supply such as a battery, due to the costs associatedwith such systems. While not preferred, it will be appreciated thatactive electrical indicator elements are also envisioned within thescope of the present invention.

[0037] Typically, electrical indicator elements comprise one or moreelectrical circuits disposed on or within the body of the microfluidicdevice. The electrical circuits are typically oriented to contact two ormore electrical contacts disposed upon the nesting region of thecontroller instrument, so as to complete an electrical circuit betweenthe two or more contacts. The indicator function of the electricalindicator elements is optionally provided by the number and identity ofdifferent circuits that are completed when the device is inserted intothe nesting region. Specifically, the pattern of electrical circuitsconnects a distinct set or subset of electrical contacts in the nestingregion to yield an electrical signature that is indicative of thefunctionality of the device used. Alternatively, the specific resistanceor conductivity of the electrical circuits on the device is varied amongdifferent devices, such that this resistance level comprises theelectrical signature that is indicative of the functionality of thedevice.

[0038] Fabrication of electrical circuits into or on a device's body maybe accomplished by a number of means. For example, in some aspects,simple patterned metal layers are disposed upon an outer surface of thebody so as to contact a preselected subset of electrical contactsdisposed upon the nesting region, thereby yielding a preselectedelectrical signature when a current is applied to the electricalcontacts. Alternatively, integrated circuits may be attached to ordisposed within the body structure of the device. Such integratedcircuits generally permit a greater complexity of available electricalsignatures using combinations of specific circuits and relativeresistances to provide the signature.

[0039] In certain aspects, an electrical indicator element may providean indication to the instrument as to whether the microfluidic devicehas been previously used or the nature of any previous use. As a resultof a previously used device, an instrument may refuse to operate, or itmay prompt the user as to the desirability of using a previously useddevice. In a preferred aspect, this type of electrical indicator elementcomprises one or more electrical circuits, e.g., as described above,except that one or more of the circuits functions as a modifiable fusedlink. In operation, following the use of the device, the instrumentsends a programmed electrical surge or other signal through the circuitor circuits of interest, resulting in modification of the fused link andof the electrical circuit. For example, such fused links may beseverable via the electrical signal, resulting in severance of theelectrical circuit. In multi-use devices, several such links may beprovided, each being severed after a subsequent use, until therecommended number of uses has been carried out. Alternatively, suchfuses may be simply modified via the electrical signal, e.g., having analtered electrical signal, e.g., resistance or the like.

[0040] One example of an electrical indicator element is illustrated inFIG. 5. As shown, a microfluidic device 500 is provided attached to thebottom surface 504 of a holder assembly 502 (see U.S. Pat. No.6,251,343) which doubles as an overall body structure. The reservoirs506-528 of the device 500 communicate via ports 530-552 to the uppersurface of the holder assembly 504. As shown, the holder assembly 502includes an array of electrical contact pads 554-564. These contact padsare positioned to contact a similar set of contact pads in the nestingregion of a controller/detector instrument (not sown).

[0041] Upon the body structure/holder assembly 502, electrical circuits,e.g., circuits 566 and 568, are provided connecting different pairs orsets of the electrical contact pads 554-564. As shown, these circuits566 and 568 comprise metal patterns that are fabricated onto the bottomsurface 504 of the holder assembly 502. When inserted into the nestingregion, the instrument, via its electrical contact pads, applies a lowlevel current through the electrical circuits 566 and 568, on the holderassembly 502. The specific pattern of the electrical circuits isidentified by the instrument, e.g., by virtue of the presence or absenceof current between two separate contact pads, the level of resistance ofthose circuits, or both. By way of example, in the device shown in FIG.5, an electric current could be applied between contact pads 554 and558, e.g., via circuit/wire 566, and between pads 562 and 564, viacircuit/wire 568. However no other currents could be applied or detecteddue to the lack of an existing circuit. Additionally or alternatively,the electrical resistance in the existing circuits is optionally variedas an indicator function. This increases the variability of thesignaling function.

[0042] As noted above, one or more of the electrical circuits, e.g.,wires 566 and 568 comprises a fused link. Such fused links are generallyprovided such that a known level of electrical current will excessivelyheat the wire, resulting in its melting and severing. These circuitcompositions are well known to those of skill in the electronics arts.

[0043] Although illustrated as an array of contact pads connected bywires or metal traces, it will be appreciated that in preferred aspects,an integrated circuit is used to provide the electrical circuits on thebody of the device. Specifically, the complexity of circuits availablethrough IC technology allows substantially greater variability in anelectrical indicator element. Further, such ICs are readily incorporatedinto the body of the devices of the invention, e.g., in the same fashionthe microfluidic device substrate is attached to the holder assembly 502in FIG. 5. Electrical interaction with the nesting region is thenaccomplished in the same fashion as shown in FIG. 5, or alternatively,through the inclusion of electrical connector pins, i.e., as typicallyused in the electronics industry for connecting ICs to circuit boards.

[0044] In a further aspect, the indicator element fabricated into orotherwise disposed on the body of the microfluidic device comprises anoptical indicator element. As used herein, an optical indicator elementis an element that is optically detected by the instrument. Again, aswith the electrical indicator elements described above, optical elementsmay be passive or active, e.g., emitting detectable light levels.Typically, however, passive optical indicators are preferred. Oneexample of a particularly preferred type of optical indicator element isa bar code that is affixed to or otherwise attached or fabricated ontothe microfluidic device's body structure. Specifically, bar codes may bereadily employed as indicators of the particular assay or otherfunctionality of the microfluidic device being used. Instruments used inconjunction with those devices that incorporate include detectionsystems for detecting the optical indicator elements. In the case of barcodes, suitable and well known bar code readers are incorporated intothe instrument and oriented to read the device's bar code from the bodyof a device inserted into the nesting region of the instrument.

[0045] An example of a device incorporating an optical indicator elementis schematically illustrated in FIG. 6. As shown in panel A, the device600 includes a bar code 602 disposed on an upper surface 604 of thedevice 600. As shown in panel B, when the device 600 is inserted intothe nesting region 652 of an instrument 650, a detector 654 foroptically detecting the bar code 602 is placed adjacent to the bar code602. The detector 604 scans and detects the bar code and relays theinformation embodied within the code to the instrument 650, indicatingthe functionality of the device 600 to the instrument 650.

[0046] Examples of chemical indicator elements include reservoirs, wellsor the like incorporating detectable chemicals, e.g., fluids havingpredefined ionic strengths, pH, and the like, which are indicative of afunctionality of the device itself.

[0047] All publications and patent applications are herein incorporatedby reference to the same extent as if each individual publication orpatent application was specifically and individually indicated to beincorporated by reference. Although the present invention has beendescribed in some detail by way of illustration and example for purposesof clarity and understanding, it will be apparent that certain changesand modifications may be practiced within the scope of the appendedclaims.

What is claimed is:
 1. A microfluidic device, comprising: a bodystructure configured to interface with a base instrument, the bodystructure having microfluidic elements disposed therein; and anindicator element fabricated into the body structure, the indicatorelement providing an indication to an instrument of a functionality ofthe microfluidic device.